Wide open in WT+ (Still selling 4 seats in the cheapest WT+ bucket: W/9 E/9 T/4)
Quite open in Economy (Selling in M class which is 2/3 of the way up to full fare). Incidentally that means Economy is more expensive than WT+ on this flight at the moment.
Quite full in CW: J/9 C/7 D/0 R/0

So my view:
- Unlikely to see further CW redemptions open on this flight
- Unlikely at short notice that WT will fill so much that it would trigger OpUps into WT+ (and pushing you to CW in the process). And for that you would have to be a Gold probably.
- Your best option is to buy the upgrade at the airport.

That said, it is only a 7h flight, perfectly bearable in WT+ and as long as your outbound is in CW, I would not spoil my anniversary trip by constantly checking for upgrade availability by the pool! Then make the decision on the spur of the moment once you reach the airport...